Here is my last problem I am having problems with: A solid ball of mass 1.70kg and diameter 16.0cm is rotating about its diameter at 65.0rev/min. What is its kinetic energy ? Ok so KE for rotation is : 1/2*I *w^2 so I found I with m *r2 and then plugged everthing into the Ke equation but didnt get it right. I converted everything and divided the diameter by 2. What could I be doing wrong??